首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Summary: Magnetic nanoparticles have been prepared by a co‐precipitation method and modified with methacryloxypropyltrimethoxysilane. Magnetic molecularly imprinted polymer particles have been prepared by suspension polymerization in silicone oil. The particles possess a high affinity to the template molecules and are rapidly separated under a magnetic field.

SEM photograph of magnetic MIP particles.  相似文献   


2.
A novel approach has been explored to prepare brain‐like polyaniline (PANI) nanostructures with many convolutions (140–170 nm in average diameter) using aniline/citric acid (CA) salt as the template and chlorine gas as the oxidant by a gas/solid reaction for the first time. The method provided here differs significantly from the traditional one in which the polymerization of PANI is usually carried out in acidic solution.

  相似文献   


3.
Hydrophilic (co)polymers carrying a thiocarbonyl thio end group such as poly(dimethylaminoethyl methacrylate), poly(ethylene oxide), and poly(ethylene oxide)‐block‐poly(dimethylaminoethyl methacrylate) have been evaluated as precursors of stabilizers in batch ab initio emulsion polymerization of styrene under acidic conditions to form electrosterically stabilized polystyrene latex particles. As a mixture of P(DMAEMA/H+Cl)‐RAFT and PEO‐RAFT failed to give satisfactory results, PEO‐RAFT was used as a control agent for the RAFT polymerization of DMAEMA, and the resulting block copolymer was successfully used in ab initio styrene emulsion polymerization.

  相似文献   


4.
This paper focuses on the attachment of densely grafted polymer layers (polymer brushes) to various inorganic and polymeric substrates by the “grafting to” method. A brief overview of synthesis of polymer brushes by the method is first provided, with emphasis on chemical approaches to polymer attachment. The second part of the paper covers the synthesis of polymer layers via a recently developed macromolecular anchoring layer approach. Several examples of application of the grafting technique are presented for generation of hydrophobic, hydrophilic, gradient, and switchable surfaces.

  相似文献   


5.
Summary: Two series of hyperbranched conjugated polymers were synthesized via an A3 + B2 type Wittig reaction. The molecular weights of the polymers were successfully tuned by simply changing the feed ratio of the monomers. Polymers with higher molecular weights presented more efficient photoluminescence, higher thermal stability and higher performance of LEDs.

  相似文献   


6.
Conformational changes in cyclic and linear chains triggered by increasing chain stiffness are explored using MC simulations. The transition to the rigid strained objects is continuous and steeper for cycles. Circular macromolecules of contour length equal to ≈5 persistence lengths are characterized as rigid strained objects with a lowered spatial dimensionality. The coil regime is almost omitted in the static structure factor already for semiflexible chains of both architectures and the flattening of stiffer cycles is evidenced by oscillations superimposed on the rod‐like behavior of corresponding linear chains. The orientational correlation function shows qualitative difference in behavior of cyclic and linear chains.

  相似文献   


7.
Summary: We describe an interesting approach to the fabrication of wettability gradients from hydrophobicity to superhydrophobicity in low‐density polyethylene (LDPE) films by first forming high porosity surfaces and placing the specimens onto linear temperature gradients. While the polymer chosen for the study is non‐polar, its microporous layer provides sufficient superhydrophobicity. Lateral gradient heating of the layer results in partial melting of the polymer and correspondingly decreases porosity thus decreasing hydrophobicity.

  相似文献   


8.
Poly(methyl methacrylate) nanosize particles were synthesized by a differential microemulsion polymerization process. Sodium dodecylsulfate and ammonium persulfate were used as the surfactant and initiator, respectively. The effects of reaction conditions on the particle size have been investigated. A particle size of less than 20 nm in diameter has been achieved with surfactant/monomer and surfactant/water weight ratios of 1:18 and 1:120, i.e. much milder conditions than those previously reported in the literature.

TEM image of nanoparticles prepared via differential microemulsion polymerization.  相似文献   


9.
Polysilsesquioxane nanosheets with a thickness of four nanometers and lateral dimensions of several hundreds of nanometers were synthesized by polymerization of a trifunctional monomer in the layer space of montmorillonite as the confined environment.

AFM image of a polymethylsilsesquioxane nanosheet.  相似文献   


10.
11.
12.
Summary: This contribution describes the graft polymerization of polystyrene (PS) by atom transfer radical polymerization at 50, 60, and 75 °C. Thick PS brushes were grown from initiator‐functionalized PGMA layers on silicon, and constant growth rates provide indirect evidence that the polymerizations were controlled.

Formation of polystyrene brushes at T < Tg by ATRP of styrene from α‐bromoester initiator‐functionalized poly(glycidyl methacrylate) layers.  相似文献   


13.
This study describes a new strategy to improve the performance of PEMFCs by the addition of S/CNF. The presence of 2.08 vol.‐% S/CNF increased the proton conductivity of a S/EPDM by one order of magnitude, which made it comparable to that of Nafion® 117, and without creating an electronic path. Furthermore, the filled membranes showed improved thermal stability and mechanical properties.

  相似文献   


14.
Transparent film materials with excellent mechanical and thermal properties were elaborated by drying a latex suspension of armored polymer/Laponite composite particles. Low‐temperature TEM observation of ultrathin cross‐sections of the films indicated a unique network morphology characterized by a “honeycomb” distribution of the Laponite platelets remindful of the original particles morphology.

  相似文献   


15.
Summary: We show in this communication that large‐scale necklace‐like single‐crystalline tetragonal perovskite PbTiO3 nanowires can be obtained via a simple electrospinning method. The morphology and the crystal structure are investigated by SEM, XRD, and HRTEM. The length of the necklace‐like PbTiO3 nanowires is from tens to several tens of micrometers, the wider the diameter of it is between 100 and 200 nm and the thinner the part is between 20 and 50 nm. The necklace‐like PbTiO3 nanowires exhibit high surface photovoltage under the action of external electric field, which is probably applicable in displaying photoelectric devices of heterojunction structure.

SEM image of the electrospinning necklace‐like PbTiO3 nanowires.  相似文献   


16.
17.
The problem of the delayed crosslinking arising due to the diffusion of a crosslinker molecule from a vector particle within a thermoset polymer matrix is discussed. The crosslinker molecules, initially embedded in the vector particles, diffuse from the particle to the polymer matrix and react with the functional groups grafted to polymer chains. The two‐step diffusion crosslink kinetics is studied theoretically on the example of polyethylene functionalized with anhydride groups reacting with 1,4‐butanediol as a crosslinker molecule. This provides the independent of time limiting distribution functions of the concentration of crosslinks, unreacted and intermediate functional groups, which are shown to be rather sensitive to system parameters as rates of chemical reactions, ratio of diffusion coefficients of matrix to vector particles, stoichiometric composition of the reactive groups, etc. The nonmonotonic distribution of the crosslink concentration around the vector particles at certain range of the parameters is revealed.

  相似文献   


18.
The complexation of bile acids with various solvated polycations was studied. A one‐to‐one complex was precipitated when an aqueous solution of cholic acid sodium salt (CA) was mixed with aqueous solutions of 3,3‐ionene and grew to form crystals with needle‐like morphology, 3 millimeters in length. Hydrogen bonding of hydroxyls at the steroid face and the spacing between cationic sites of polycations were crucial for the formation of the giant needle.

Crossed polarizing microscopic photograph of the complex composed of cholic acid sodium salt and 3,3‐ionene.  相似文献   


19.
The polymerization kinetics of a RAFT‐mediated radical polymerization inside submicron particles (30 < Dp < 300 nm) is considered. When the time fraction of active radical period, ϕA, is larger than ca. 1%, the polymerization rate increases with reducing particle size, as for the cases of conventional emulsion polymerization. The rate retardation by the addition of RAFT agent occurs with or without intermediate termination in zero‐one systems. For the particles with Dp < 100 nm, the statistical variation of monomer concentration among particles may not be neglected. It was found that this monomer‐concentration‐variation (MCV) effect may slow down the polymerization rate. An analytical expression describing the MCV effect is proposed, which is valid for both RAFT and conventional miniemulsion polymerizations.

  相似文献   


20.
Au nanoparticles (NPs) and polymer composite particles with phase‐separation structures were prepared based on phase separation structures. Au NPs were successfully synthesized in amphiphilic block‐copolymer micelles, and then composite particles were formed by a simple solvent evaporation process from Au NPs and polymer solution. The phase separated structures (Janus and Core‐shell) were controlled by changing the combination of polymers having differing hydrophobicity.

  相似文献   


设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号